1. Field of the Invention
The invention relates to a method for producing liquid metal, in particular pig iron or liquid steel preproducts, from charging substances comprised of ore, in particular iron ore, and of fluxes, wherein the ore is directly reduced to sponge metal in at least one reduction zone, the sponge metal is melted along with fluxes in a melt-down gasifying zone under the supply of carbon carriers and of an oxygen-containing gas and a CO- and H.sub.2 -containing process gas serving as a reducing gas is produced which is fed into the reduction zone and is reacted there and subsequently is withdrawn, wherein slagforming fluxes, in particular calcium carbonate, dolomite etc., by means of the process gas are calcined in a calcining zone that is separate from the reduction zone and melt-down zone and to a plant for carrying out the method.
2. Brief Description of the Related Art
It is known to admix slag formers such as CaCO.sub.3, dolomite etc. to the ore and effect calcination at the same time and in the same vessel as the reduction of the ore, i.e. in the reduction zone, wherein calcination is effected by means of the reducing gas. With a multistage reduction process, i.e. with a method in which several reduction zones are provided which are subsequently connected in series, complete calcination is effected only in the final reduction stage, as only in this stage the reducing gas has the temperature required for complete calcination. A disadvantage associated with this method is that the quality of the reducing gas will deteriorate, and further, that by the calcining process, which is endothermic, the reducing gas is decreased in temperature. Another disadvantage is that in the reduction of fine ore, the slagforming additions must have roughly the same grain size range so that the fluidized bed formed by the fine ore in the reduction reactor will remain largely undisturbed. Coarse-grained fluxes cannot be exploited in this manner.
From DE-A-42 40 197, a method of the initially described kind is known in which slagforming additions are treated in a separate calcining zone of a calciner, with reducing gas originating from the melter gasifier being employed for calcining purposes. In accordance with DE-A-42 40 197, the calcined fluxes are charged into the reduction reactor in the reduction zone and together with the already partially reduced ore are moved onward through the reduction shaft and finally are charged into the melter gasifier with the reduced ore.
Another disadvantage associated with this method is that the grain of the fluxes cannot be chosen freely. On the contrary, the grain or the grain size range respectively has to correspond to the grain or the grain size range respectively of the fine ore being moved through the reduction shaft. Further, an adverse effect on the reduction process, in particular on complete reduction, is to be expected, since the material and gas flow as well as the temperature profile are disturbed by the charging of the fluxes.